| Carbon fiber reinforced thermoplastic composites(CFRTPC)have been widely used in aerospace and automotive applications because of their high specific strength,high specific modulus,high wear resistance,and high stiffness.Polylactic acid(PLA)has excellent mechanical properties and biodegradability,and the raw material is derived from plants,which enables it to replace a large number of fossil fuel-based polymers.In this study,carbon fiber(CF)was used as the reinforcing material to prepare CF/PLA composites with high performance by different forming process.Firstly,short-cut carbon fiber(SCF)reinforced SCF/PLA composites were prepared by injection molding.The effects of SCF on the microscopic morphology,crystalline properties,thermal stability and mechanical properties of the composites were investigated.The results show that the dispersion of SCF in the composites was good when the content of SCF is lower than 40 wt%,and the crystallization ability of the composites became stronger with the increase of SCF content.Meanwhile,the mechanical properties were the best,with tensile strength of 159.9 MPa,Young’s modulus of 20.5 GPa,which were 1.2 and 4.9 times higher,respectively,compared to pure PLA,and flexural strength and modulus of 209.6 MPa and 23.3 GPa,respectively.90% and 5.4 times higher,respectively,compared to pure PLA.Secondly,CFF/PLA-VARTM composites were prepared by in situ ring-opening polymerization of L-Lactide propyl ester(L-LA)via vacuum-assisted resin transfer molding(VARTM)process using carbon fiber fabric(CFF)as the filler.For comparison,CFF/PLA-CM composites were also prepared by hot pressing process.The effects of different forming process on the structure,morphology,crystalline properties and mechanical properties of the composites were investigated.The results showed that CFF/PLA-VARTM had excellent interfacial adhesion.A trans-crystalline layer(TCL)structure was observed due to the PLA sheet crystals growing perpendicularly around the fiber axis.The crystallinity of PLA in CFF/PLA-VARTM composites was significantly higher,4.1 times higher than that of pure PLA.Compared with pure PLA and the CFF/PLA-CM composite,the tensile strength of the CFF/PLA-VARTM composite reaches 502.1 MPa,increased by 7.5 times and 1.4times higher,respectively,and the tensile modulus reaches 31.3 GPa,increased by13.7 times and 78%,respectively,and the bending strength and bending modulus of the composites showed the same trend.Finally,CFF/PLA/TPU shape memory composites were prepared by in situ ring-open polymerization method via VARTM process.Their structure,microscopic morphology,crystalline properties,mechanical properties,and shape memory properties were investigated.The results showed that the CFF/PLA/TPU composites still had good interfacial bonding.When the mass fraction ratio of TPU to PLA was10:90,the tensile strength and Young’s modulus of CFF/PLA/TPU composites were403.7 MPa and 29.4 GPa,respectively,which were 7.9 times and 16.2 times higher than those of PLA/TPU alloy with the same TPU content.Meanwhile,the CFF/PLA/TPU composites exhibited excellent shape memory properties. |
